Technical Field
The present disclosure relates to a bus microcontroller and a bus node circuit comprising a bus microcontroller. Such a bus microcontroller and bus node circuit are used in particular for coupling to a communication bus for a vehicle for realizing so-called “partial networking”. This is for example a CAN bus microcontroller that is adapted to be coupled to a CAN communication bus. The disclosure moreover relates to an electronic control unit (“ECU”) for a vehicle comprising a bus microcontroller and a bus node circuit, respectively.
Description of the Related Art
A communication bus, such as, e.g., in a vehicle, is typically coupled to a plurality of electronic control units (ECUs) performing various functions and constituting a respective bus node. For example, there is provided an ECU for door control and/or an ECU for trunk control, by means of which closing and opening, respectively, of the doors and the trunk respectively, can be controlled and monitored. Such ECUs, in terms of the function thereof, can be subdivided into groups and can be allocated to different functional groups (so-called “domains”). For example, there is a “body domain” related to functions for user convenience, a “chassis domain” related to user safety, and an “infotainment domain” related to information and entertainment, etc. Each of these domains may have a communication bus of its own, for example in the form of a controller area network (CAN) bus, to which the ECUs of the corresponding modules to be controlled are connected as bus participants. Each such ECU to this end comprises a bus node circuit via which a bus microcontroller of the ECU is coupled to the bus and adapted to communicate with a central bus control module (e.g., a so-called “body control module” (BCM) for the body domain) which controls and monitors data traffic on the communication bus. In accordance with a further example, bus communication can also take place in a decentralized fashion without a central bus control unit.
A bus microcontroller of an ECU, such as of a door controller, receives a bus message, e.g., via the communication bus to the effect that a window of the door is to be opened. The bus microcontroller then performs a so-called task (i.e., a process), addressing a corresponding circuit for opening the windows. A frequently used communication bus for such purposes is the known CAN communication bus.
An increasing trend in modern vehicles is that the number of functional units, and thus the number of ECUs, increases with increasing number of convenience and safety functions in the vehicle. A problem associated therewith, however, consists in that, with an increasing number of ECUs in the vehicle, the energy consumption for operating the ECUs increases as well. These are not only operated with electrical energy when the function is active, but also during other times while they are passive and do not drive a functional circuit for performing a specific function, such as opening the windows. This causes the energy consumption of the vehicle and the CO2 emission of the same to rise.
There are technologies in existence at present which permit the energy consumption of ECUs to be reduced in the so-called “standby mode” in which no function is performed. Such a technology is known for example as so-called “partial networking” in which a bus participant, such as a bus microcontroller of an ECU, is switched into an active or inactive state, respectively, for a certain period of time. In general, “partial networking” describes the function of activating a specific part of a network at a specific point of time. For example, the protocol of the CAN bus (CAN stands for control area network) supports “partial networking” for vehicle components that are connected to the CAN bus. In this regard, e.g., the bus microcontroller recognizes a state in which it can switch to an inactive state, e.g., when the vehicle is parked and a window is not to be opened for a longer period of time. For example, the BCM of the vehicle transmits a corresponding message on the communication bus, which is recognized by the ECU and the bus microcontroller of the door controller, respectively, and the bus microcontroller as a result is switched to the inactive state. However, when a bus message is addressed to an ECU, it has to be served by the corresponding bus microcontroller of the ECU. For example, it is necessary to operate and initialize internal memories to this effect. This may prevent the bus controller from entering a standby mode.
An approach of “partial networking,” e.g., provides that the bus microcontroller of an ECU controls a voltage supply circuit which then deactivates the supply voltage of the bus microcontroller. The result of this is that the bus microcontroller consumes no electrical energy in this state. If the transmitter-receiver circuit (so-called “transceiver”) of the ECU receives a message on the bus and recognizes that the bus controller is to be activated (in particular by a so-called “wake-up” message having a specific pattern and defining a so-called “wake-up event” and consequently a specific activation action), the transceiver controls the voltage supply circuit whereupon the latter reactivates the supply voltage of the bus microcontroller. This may also include the supply voltage of additional components of the ECU.
An aspect to be considered in this regard is that the bus microcontroller, upon activation of the supply voltage, needs a relatively long period of time to get started and to load all necessary software routines in the internal memories (i.e., so-called booting process). Such a booting process has a duration, e.g., in the order of 100 ms. However, this prevents the bus microcontroller from turning off also during times in which it is actually inactive, but is still logged on or registered to the central bus control module (BCM) as active bus participant (e.g., at times when no window opening operation is performed during vehicle travel). For, with the occurrence of an event, such as operation of the power window, the reaction period from booting of the microcontroller to opening of the window would be too long.
It would also be conceivable in such “inactive” periods of time to utilize the bus microcontroller in such times, in which it does not participate in bus traffic, for other functions, e.g., for contact monitoring of switch contacts, such as the switches for the power windows. Such contact monitoring could take place approximately in time intervals of 50 ms. Due to the long booting duration of the bus microcontroller, however, it is not possible to boot the microcontroller each time for an individual contact monitoring operation, as this period of time would be considerably longer than the monitoring interval. This has the effect that the bus microcontroller, for such contact monitoring, has to remain in the active state so that the energy consumption cannot be lowered for such application either.
It would be desirable to make available a bus microcontroller and a bus node circuit for a communication bus comprising a bus microcontroller which, in connection with the “partial networking” functionality of a bus network, permits a further reduced energy consumption to be achieved.